11

LT1611

TYPICAL APPLICATIO S

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However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-

tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.

Table 1. Inductor Vendors

VENDOR

PHONE

URL

PART

COMMENT

Sumida

(847) 956-0666

www.sumida.com

CLS62-22022

22

µH Coupled

CD43-470

47

µH

Murata

(404) 436-1300

www.murata.com

LQH3C-220

22

µH, 2mm Height

Coiltronics

(407) 241-7876

www.coiltronics.com

CTX20-1

20

µH Coupled, Low DCR

Table 2. Capacitor Vendors

VENDOR

PHONE

URL

PART

COMMENT

Taiyo Yuden

(408) 573-4150

www.t-yuden.com

Ceramic Caps

X5R Dielectric

AVX

(803) 448-9411

www.avxcorp.com

Ceramic Caps

Tantalum Caps

Murata

(404) 436-1300

www.murata.com

Ceramic Caps

Capacitors

As described previously, ceramic capacitors can be used

with the LT1611 provided loop stability is considered. For

lower cost applications, small tantalum units can be used.

A value of 22

µF is acceptable, although larger capacitance

values can be used. ESR is the most important parameter

in selecting an output capacitor. The “flying” capacitor (C2

in the schematic figures) should be a 1

µF ceramic type. An

X5R or X7R dielectric should be used to avoid capacitance

decreasing severely with applied voltage. The input by-

pass capacitor is less critical, and either tantalum or

ceramic can be used with little trade-off in circuit perfor-

mance. Some capacitor types appropriate for use with the

LT1611 are listed in Table 2.

Diodes

A Schottky diode is recommended for use with the LT1611.

The Motorola MBR0520 is a very good choice. Where the

input to output voltage differential exceeds 20V, use the

MBR0530 ( a 30V diode). If cost is more important than

efficiency, a 1N4148 can be used, but only at low current

loads.

OPERATIO

3.3V

–5V

70mA

1611 TA02

SW

L1

10

µH

D1

D2

GND

LT1611

C1, C2: TAIYO YUDEN LMK212BJ105MG

C3: TAIYO YUDEN JMK325BJ226MM

D1, D2: MBR0520

L1: MURATA LQH3C-100

C1

1

µF

C3

22

µF

C2

1

µF

10k

29.4k

NFB

SHDN

“Charge Pump” Inverting DC/DC Converter